The present method is well suited for timing engines, particularly fuel injected engines such as diesel engines.
Many mechanisms, such as diesel engines for example, have parts which cooperate in time relation to produce optimum performance. An improperly timed engine wastes fuel and increases exhaust emissions. The energy crisis has helped create a need for increased fuel economy and environmental concern has increased the need to measure timing more accurately.
Conventional timing methods normally include attaching transducers to the engine or apparatus to be timed, generating first and second timing signals, and measuring the period between the timing signals. The second signal is normally representative of the top dead center position of the number one piston as indicated by a hole or slot in the flywheel which is connected to the crankshaft. The first signal occurs when a pressure pulse appears in the fuel line leading to the number one cylinder in a diesel engine or when a spark appears leading to the number one spark plug in a regular engine.
Measuring the period between the first and second signals produces an erroneous timing measurement because such measurement does not detect instantaneous changes in crankshaft speed caused by piston firing and crankshaft loads. Measuring the period between the timing marks assumes constant angular rotation of the crankshaft when torsionals of half a degree can occur on the crankshaft. Measuring the period between the timing signals requires greater resolution between the signals when large angles are to be measured. It is therefore desirable to have a timing method which detects instantaneous changes in crankshaft speed and which does not require increased resolution for measuring large angles.